研究了Bi--6\%Mn合金从低于446℃开始的半固态凝固过程中, MnBi析出相磁致织构的形成过程和规律. 结果表明, 合金从355$\sim$446℃开始半固态凝固时, 合金中的MnBi相在340℃(MnBi相顺磁--铁磁转变温度)附近发生形态突变, 由规则的六方晶体转变为沿ab面长大的不规则片状晶体; 析出相的磁致织构是在发生磁性转变生成铁磁性MnBi相后通过晶粒旋转取向形成的. 合金从低于355℃开始半固态凝固, 导致织构形成的磁感应强度阈值随着温度的升高而降低, 从355$\sim$446℃之间开始的半固态凝固则相反. 磁场中合金从低于355℃开始的半固态凝固有利于制取高性能的过共晶Bi/MnBi磁性复合材料.
Magnetic textured structures of MnBi precipitated phase in Bi--6\% Mn alloy were studied experimentally during solidification of the alloy from the semi solid zone below 446℃. An abrupt shape change of MnBi phase from regular hexagonal grains to oblate grains grown up along their ab--plane was observed firstly near 340℃, which is the transformation temperature of MnBi compound from paramagnetic state to ferromagnetic state. After the production of ferromagnetic MnBi grains from the magnetic transformation, the textured structures form by the rotation of the precipitated grains. The critical magnetic flux intensity for the textured structures decreases with increasing the heating temperature during solidification from the semi solid zone below 355℃ and increases between 355℃ and 446℃. Solidification from the semi solid zone below 355℃ is propitious to fabricate hypereutectic Bi/MnBi magnetic composites with excellent properties.
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